BURNS, Ore. — A group of armed anti-government activists remained encamped at a federal wildlife refuge in Oregon on Sunday evening, vowing to occupy the outpost for years to protest the federal government’s treatment of a pair of local ranchers set to report to prison Monday.

The occupation of a portion of the Malheur National Wildlife Refuge, about 30 miles southeast of Burns, Ore., began a day earlier, after a small group of men broke off from a much larger march and rally held on Saturday evening

The armed occupation is being led by Ammon Bundy, an Idaho rancher whose father, Cliven Bundy, led an armed standoff with federal agents in Nevada in 2014 and who has described his supporters as “militia men.”

“Those who want to go take hard stand, get in your trucks and follow me!” Ammon Bundy declared to rally-goers at the conclusion of Saturday’s event, according to several people who were in attendance. Not long afterward, the group had taken over the federal wildlife preserve.

Harney County Sheriff David M. Ward said authorities from several law enforcement organizations were monitoring the ongoing incident.

“These men came to Harney County claiming to be part of militia groups supporting local ranchers,” Ward said in a statement Sunday. “When in reality these men had alternative motives, to attempt to overthrow the county and federal government in hopes to spark a movement across the United States.”

Organizers of the rally say several hundred attended the procession through Burns, Ore. — a ranching town of less than 3,000 residents — in a show of support for Dwight Hammond, 73, and his son Steven Hammond, 46, who in the conclusion of a decades of clashes with the federal government were sentenced last October to serve five years in prison.

Prosecutors accused the Hammonds of committing arson on federal land in 2001 and 2006. The men and their attorneys argued that the fires had been set on their own property — once to prevent the spread of an invasive species of plant and once in attempt to prevent the spread of a wildfire — and had inadvertently burned onto public lands. But prosecutors said the fires were set in attempt to destroy evidence that the Hammonds had been illegally hunting deer on the federal lands.

The two men have previously served prison time for the crimes, but earlier this year a federal appeals court concluded that their initial sentences had been too short — arson on federal property carries a mandatory minimum sentence of five years — and ordered the men back to prison.

“We all know the devastating effects that are caused by wildfires. Fires intentionally and illegally set on public lands, even those in a remote area, threaten property and residents and endanger firefighters called to battle the blaze” stated Acting U.S. Attorney Billy Williams,in a statement issued after the Hammonds were sentenced. “Congress sought to ensure that anyone who maliciously damages United States’ property by fire will serve at least 5 years in prison. These sentences are intended to be long enough to deter those like the Hammonds who disregard the law and place fire fighters and others in jeopardy.”

At a news conference on Sunday, Ammon Bundy said his group had not heard from law enforcement since taking over the unoccupied site and urged other citizens from across the country to join their effort.

If a standoff resulting in violence occurs, Bundy said, it would begin on the government’s side.

“This refuge here is rightfully owned by the people and we intend to use it,” he said, adding that they plan to assisting ranchers, loggers, hunters and campers who want to use the land. “We will be here as a unified body of people that understand the principles of the Constitution.”

The occupation of the wildlife refuge, which was not occupied when stormed by the men, comes at the conclusion of a lively weekend for an otherwise sleepy stretch of southeast Oregon.

Snowdrifts and miles of desolate highway studded with sagebrush and tumbleweed separate Burns, Ore., near the refuge, from Boise, Idaho, the nearest big city, which is about 220 miles away. Little traffic was headed toward Boise on Sunday evening, but regulars at the Oasis, a restaurant in Juntura, Ore., said groups of travelers coming from Idaho had been stopping for food and gas on the way to Burns, where they hoped to lend support to the protesters. They didn’t want to talk about it too much. The subject was too sensitive, they said.

Along the 60 miles from Juntura – more a restaurant stop than a town – to Burns, ranches could be spotted about every 20 miles or so among the rolling hills, along with horses and cattle. It was just below freezing, with nighttime lows headed toward 13 degrees.

Noting that the group isn’t holding hostages, Ryan Bundy, who is also involved in the siege, echoed his brother, telling the Oregonian that the group doesn’t want to resort to violence but will not rule it out if authorities attempt to remove the occupiers from the property.

The group is calling for the Hammonds’ release and said the militia was planning an occupation that lasted “for years.”

“The best possible outcome is that the ranchers that have been kicked out of the area, then they will come back and reclaim their land, and the wildlife refuge will be shut down forever and the federal government will relinquish such control,” Ryan Bundy told the Oregonian. “What we’re doing is not rebellious. What we’re doing is in accordance with the Constitution, which is the supreme law of the land.”

One tearful occupier, expecting not to come home, recorded a video railing against the Hammonds’ sentence and saying goodbye to his family. He said he was trying to win the “hearts and minds” of Oregonians.

One of the militia men occupying the fed wildlife refuge in OR left a goodbye video to his family. https://t.co/GIg65GbieV

The Malheur National Wildlife Refuge was established Aug. 18, 1908, by President Theodore Roosevelt “as a preserve and breeding ground for native birds,” according to the park’s website.

“The Refuge represents a crucial stop along the Pacific Flyway and offers resting, breeding, and nesting habitat for hundreds of migratory birds and other wildlife,” a statement on the site says. “Many of the species migrating through or breeding here are highlighted as priority species in national bird conservation plans.”

At Sunday’s news conference, Ammon Bundy said the refuge’s creation was “an unconstitutional act,” one that removed local ranchers from their lands, thrusting the county into an economic depression.

In a video interview with reporters on Saturday that was posted on his Facebook page, Ammon Bundy said the group is standing up against government “overreach” because “the people have been abused long enough.”

“I feel we are in a situation where if we do not do something, if we do not take a hard stand, we’ll be in a position where we’ll be no longer able to do so,” he said.

Ammon Bundy told the Oregonian that he and two of his brothers were among a group of dozens of people occupying the headquarters of the Malheur National Wildlife Refuge. (Les Zaitz/the Oregonian via AP)

A video posted days earlier on Bundy’s Facebook page urged militia members from all over the country to join him:

“**ALL PATRIOTS ITS TIME TO STAND UP NOT STAND DOWN!!! WE NEED YOUR HELP!!! COME PREPARED.”

Beth Anne Steele, an FBI spokeswoman in Portland, told the AP that the bureau was aware of the situation at the wildlife refuge, but she declined further comment.

A U.S. Fish and Wildlife Service spokesperson told CNN that the agency and the Bureau of Land Management are monitoring the armed protesters.

“While the situation is ongoing, the main concern is employee safety, and we can confirm that no federal staff were in the building at the time of the initial incident,” the spokesperson said. “We will continue to monitor the situation.”

“That’s not exactly what I thought should happen, but I didn’t know what to do,” he said. “You know, if the Hammonds wouldn’t stand, if the sheriff didn’t stand, then, you know, the people had to do something. And I guess this is what they did decide to do. I wasn’t in on that.”

Late Saturday, the occupiers blocked the entrance of the federal headquarters with a pickup truck and placed an American flag over the welcome sign, according to Oregon Public Broadcasting. An Oregon State Police car “idled by the side of the road just outside Burns,” the broadcaster reported, but there were no signs of a larger law enforcement presence in the area.

“We are not hurting anybody or damaging any property.,” Ammon Bundy told OPB. “We would expect that they understand that we have given them no reason to use lethal force upon us or any other force.”

Ron Gainer, the owner of a nearby RV park who dropped off some chili for the occupiers, told the broadcaster that he counted about 15 people, a half-dozen vehicles and a trailer at the site. The estimate differed sharply from the Bundy family accounting, which put the number of people at the refuge at about 150, according to OPB.

By nightfall, the broadcaster noted, the temperature had plummeted to 10 degrees, prompting occupiers to bundle around a campfire. Some of those present identified themselves as nearby residents and supporters of the convicted ranchers.

Asked by an OPB reporter how many militia members were at the headquarters, Bundy didn’t divulge.

“I will not disclose,” he said. “Operational security.”

[This is a developing story and will continue to be updated. Holley and Lowery reported from Washington.]

Peter HolleyPeter Holley is a technology reporter at The Washington Post. Before joining The Post in 2014, he was a features writer at the Houston Chronicle and a crime reporter at the San Antonio Express-News. Follow

Wesley LoweryWesley Lowery is a national correspondent covering law enforcement, justice and their intersection with politics and policy for The Washington Post. He previously covered Congress and national politics. In 2015, he was a lead reporter on the "Fatal Force" project awarded the Pulitzer Prize and George Polk award. Follow

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